There are prior art arrangements which use an adjusting screw for adjusting a doctor blade structure relative to a toner carrying cylindrical member. Such arrangements use an adjusting screw that acts directly on the doctor blade to determine its position relative to the toner carrying member. Depending on the pitch of the adjusting screw threads, each revolution of the adjusting screw will provide movement of the doctor blade structure relative to the toner carrying cylindrical member in the range of 0.064 to 0.081 centimeters. This degree of adjustment is not usable for adjusting the doctor blade structure for some types of toners. The characteristics of some toners are such that a much finer adjustment control is needed than can be obtained from the use of such prior art arrangements.